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tty: Fix BKL taken under a spinlock bug introduced in the BKL split 

The fasync path takes the BKL (it probably doesn't need to in fact)
while holding the file_list spinlock.  You can't do that with the kernel
lock: it causes lock inversions and deadlocks.

Leave the BKL over that bit for the moment.

Identified by AKPM.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Acked-and-Tested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alan Cox 2009-12-12 10:32:36 +00:00 committed by Linus Torvalds
parent 09cea96caa
commit 6698e34720
1 changed files with 0 additions and 2 deletions
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2
drivers/char/tty_io.c
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@ -516,7 +516,6 @@ static void do_tty_hangup(struct work_struct *work)
/* inuse_filps is protected by the single kernel lock */ /* inuse_filps is protected by the single kernel lock */
lock_kernel(); lock_kernel();
check_tty_count(tty, "do_tty_hangup"); check_tty_count(tty, "do_tty_hangup");
unlock_kernel();
file_list_lock(); file_list_lock();
/* This breaks for file handles being sent over AF_UNIX sockets ? */ /* This breaks for file handles being sent over AF_UNIX sockets ? */
@ -531,7 +530,6 @@ static void do_tty_hangup(struct work_struct *work)
} }
file_list_unlock(); file_list_unlock();
lock_kernel();
tty_ldisc_hangup(tty); tty_ldisc_hangup(tty);
read_lock(&tasklist_lock); read_lock(&tasklist_lock);